The typical elevator governor may consist of a disc that is driven by a governor rope secured to the car of the elevator, and may include at least one flyweight mounted on the disc. The flyweight responds to excessive speed by progressively moving outward under its own centrifugal force to push against a spring force, ultimately stopping the disc at a certain speed, which abruptly stops the rope. The rope is secured to an elevator safety actuated by the governor operation to bring the elevator car or the counterweight to a safe stop.
Most regulations on the construction of elevators specify that governors should also operate at a speed increase of about 20%-40% over maximum to deenergize the elevator drive motor. Typically this is done by operating a safety switch. This operation is in addition to the operation of the mechanical safety that typically slows the elevator car and/or counterweight by engaging a guide rail when the car or counterweight moves down.
One type has a rubber roller that is mounted on a lever, and rolls over a polygon-shaped disc so that the disc may be progressively stopped when the lever is lifted or moved as a function of the disc speed.
Another type of governor has a flywheel which operates a linkage that clamps the elevator governor rope. In this device the flywheels are forced against the inside surface of the governor housing, stopping the disc and applying force to the rope.
Among the disadvantages to these and other similar governors is that the response time, that is, the time required to engage the safety after the maximum speed condition has occurred, is relatively long and also variable. In most cases the reason is that the governor disc can only be stopped at discrete angular positions. This is particularly true of governors having polygon-shaped discs. They also suffer from knocking noise, as a result of the shape of the discs. This noise is evidence of the inherent discontinuous type of operation such governors provide. These and other governors respond only to speed increase of the governor rope above a predetermined value, not to excessively high accelerations (second derivative changes).